1. Field of the Invention
The present invention relates to a method for producing a display device, and specifically relates to a process of thinning a substrate which composes a display device.
2. Description of the Related Art
In recent years, electronic appliances, household electrical appliances, or the like, have been increasingly developed and produced and have been sold in quantity on the market, and not only a TV set but also a VTR, a personal computer, and the like, have also been spread widely among ordinary people. These appliances have grown their performances year by year, and have been indispensable in our modern society as a tool for providing the users with a lot of information as the information society progresses. Many of these appliances are equipped with a display device which serves as information displaying means for accurately transmitting information to the users, and as the display device, a low-profile and lightweight display device has been desired.
For example, Japanese Unexamined Patent Publication JP-A 4-116619 (1992) (JP-B2 2722798), discloses an invention which aims at weight-reduction of liquid crystal display devices. It discloses a method of producing a liquid crystal display device, capable of obtaining a plurality of liquid crystal display devices from a pair of glass substrates, wherein in order to thin the liquid crystal display devices, chemical abrasion is performed in a state of an assembly of the liquid crystal display devices in which the pair of substrates having an area for the plurality of liquid crystal display devices are bonded.
In the following, the prior art will be briefly explained referring to drawings.
FIGS. 12 and 13 show plan and sectional views of an assembly of liquid crystal display devices. (hereinafter described as an assembly of devices) made by bonding a pair of substrates having an area for the plurality of liquid crystal display devices. The assembly of devices A is assembled in the following manner.
At first, in each region of a pair of glass substrate a transparent electrode for display, an orientation film, and the like, (not shown in the drawings) are formed on each device division 6 on a pair of original glass substrates (so-called mother glass substrates) 1, 2.
Next, frame-shaped sealing materials 3 for respectively surrounding regions b of the respective in which liquid crystal is to be sealed regions b of the respective device divisions 6 are printed on the surface of one of the original glass substrates, and a periphery sealing material 4 for surrounding all of the device divisions 6 is printed slightly inside the edge of the periphery of the glass substrate. As such an adhesive, an epoxy-resin adhesive which has a high etching selectivity ratio with the original glass substrates 1, 2 is used. Moreover, each sealing material 3 is printed so that a clearance to become a liquid crystal injection hole 3a is left on part thereof, and the periphery sealing material 4 is printed so that a clearance to become a ventilation hole 4a is left on part thereof.
Next, the pair of original glass substrates 1, 2 are stacked on each other so that the respective device divisions 6 are opposed to each other, and the original glass substrates 1, 2 are adhered to each other via the sealing materials 3 and the periphery sealing material 4 as described above. In this case, a gap between the original glass substrates 1, 2 is connected with the outside via the liquid crystal injection holes 3a provided on parts of the respective sealing materials 3 and the ventilation hole 4a provided on part of the periphery sealing material 4, so that the barometric pressure between the original glass substrates 1, 2 would not be increased. Therefore, both the original glass substrates 1, 2 are globally adhered to each other with a uniform gap.
After that, the ventilation hole 4a as mentioned above is encapsulated by an encapsulating material 5 such as an epoxy-resin adhesive which has a high etching selectivity ratio with both the original glass substrates 1, 2, whereby the assembly of devices A is completed.
After the assembly of devices A is assembled in this way, the assembly of devices A is immersed in an etchant 11 inside an etching tank 10 to etch the outer faces of both the original glass substrates 1, 2 of the assembly of devices A as shown in FIG. 14. In this case, an etchant which basically consists of hydrofluoric acid is used as the etchant 11.
When the assembly of devices A is immersed in the etchant 11 to etch the outer faces of both the original glass substrates 1, 2 in this way, the thickness of each of the original glass substrates 1, 2 is reduced from the initial thickness as shown by a dashed line to the thickness as shown by a rigid line in FIG. 14. Moreover, since etching of the original glass substrates 1, 2 is performed uniformly all over the outer faces of the substrates, the overall original glass substrates 1, 2 are thinned uniformly.
Further, when the assembly of devices A is immersed in the etchant 11, the etchant 11 would enter the gap between the original glass substrates 1, 2. However, in the production method as described above, the pair of original glass substrates 1, 2 are adhered to each other via the periphery sealing material 4 which surrounds all of the device divisions 6 when the assembly of devices A is assembled, the ventilation hole 4a provided on part of the periphery sealing material 4 is encapsulated by the encapsulating material 5, and the sealing material 4 and the encapsulating material 5 are made by an epoxy-resin adhesive, or the like, which has a high etching selectivity ratio with the original glass substrates 1, 2. Therefore, it is avoided by the periphery sealing material 4 that the etchant 11 enters the gap between the original glass substrates 1, 2.
Therefore, in etching of the outer faces of the original glass substrates 1, 2, the inner sides of the respective device divisions 6, that is, electrode terminal arrays outside the sealing materials 3 and the liquid crystal sealed-in regions b surrounded by the sealing materials 3 would not be subjected to the etchant 11. As for both the original glass substrates 1, 2, although not only the outer faces but also the periphery faces are etched, it is prevented by the periphery sealing material 4 that the etchant 11 enters the gap between the original glass substrates 1, 2 before the peripheral faces of the glass substrates 1, 2 are etched to recess inside the inner peripheral face of the periphery sealing material 4. Therefore, as long as the periphery sealing material 4 as mentioned above is printed slightly inside the edge of the periphery of the substrate and the periphery sealing material 4 is made to have a sufficient width, any problem would not be caused when the peripheral faces of the glass substrates 1, 2 are etched.
After the outer faces of both the original glass substrates 1, 2 are etched in this way in a state where the assembly of devices A is assembled, the assembly of devices A is washed immediately to thoroughly eliminate the etchant attached thereon, and thereafter both the original glass substrates 1, 2 of the assembly of devices A as mentioned above are divided for each device division 6, with the result that the assembly of devices A is separated into cell members of individual liquid crystal display devices.
After that, a liquid crystal material is injected by the vacuum injection method into the gap between the substrates of a cell member of each liquid crystal display device, and the injection hole 3a is encapsulated by an encapsulating resin, whereby a liquid crystal display device is completed. The vacuum injection method is a method of immersing an injection hole of a liquid crystal display device in a liquid crystal pool which contains liquid crystal after producing a vacuum state in a vacuum chamber, and then returning the pressure inside the vacuum chamber to the original barometrical pressure, thereby performing injection of liquid crystal. According to this method, injection of liquid crystal into a cell member of a liquid crystal display device can be performed easily and uniformly.
In the method for producing a display device as shown above, the substrates are thinned in a state of an assembly of devices using an etching tank, so that it is necessary to prepare a large etching tank, and accordingly it is also necessary to prepare a large quantity of etchant. Therefore, the production efficiency is low. Moreover, the thinned assembly of devices is hard to handle and it is apt to break when it is pulled out from the etching tank and conveyed, so that a lot of caution is required to pay.
Further, particularly in the liquid crystal display device disclosed in the prior art as shown above, injection of a liquid crystal material is performed by the vacuum injection method in a state where the substrates were thinned, so that there is a problem that the substrates are broken or chipped in the vacuum injection process.
Furthermore, although it may be considered to thin the substrates in a state of divided substrates instead of thinning the substrates in a state of an assembly of devices as described above, such a problem would be caused that throughput is worse and the production process is longer when the substrates are thinned one by one in a state of divided substrates.
The present invention was made in view of the problems as mentioned above, and an object of the invention is to provide a method for enabling to easily produce a low-profile and lightweight display device by efficiently thinning a substrate.
The invention provides a method for producing a display device which is composed by at least a pair of substrates, comprising the steps of:
forming a sealing resin layer on one original substrate having an area for a plurality of display devices, of a pair of original substrates;
bonding the other original substrate onto the one original substrate having an area for a plurality of display devices via the sealing resin layer;
dividing the pair of original substrates having been bonded to separate the pair of original substrates into a plurality of pairs of substrates having an area for each individual device; and
performing a substrate thinning process of causing substrate holding means to hold the pairs of substrates having been separated to be of a size of each individual display device and thinning at least one substrate of each pair of substrates in a state where the substrates are held by the substrate holding means.
That is to say, the other original substrate is bonded onto the one original substrate having an area for a plurality of display devices via the sealing resin layer, the pair of original substrates having been bonded is divided and separated into a plurality of substrates of a size of each individual display device, and thereafter the substrate thinning process of thinning the substrates is performed in a state where the substrates are held by the substrate holding means. As compared with a case of performing the thinning process in a state of an assembly of devices which has original substrates having an area for a plurality of display devices, it is not necessary in the invention to prepare a large etching tank, and accordingly it is not necessary to prepare a large quantity of etchant.
Further, a plurality of substrates having been separated to be of a size of each individual display device are thinned at a time while being held by the substrate holding means, so that throughput is good, and the substrate thinning process can be efficiently performed. As a result, it is possible to implement a lightweight and low-profile display device in a simple manner.
Further, in the invention it is preferable that the step of performing the substrate thinning process of thinning the substrate is performed by a chemical abrading method.
That is to say, since the substrate thinning process is performed by the chemical abrading method, it is possible to perform the substrate thinning process which causes little damage to the substrates.
Still further, in the invention it is preferable that the step of performing the substrate thinning process of thinning the substrate is performed in a state where encapsulating means is formed on an end portion of the pair of substrates having been divided to be of a size of each individual display device.
That is to say, since the step of performing a substrate thinning process of thinning a substrate is performed in a state where encapsulating means is formed on the end portion of the pair of substrates having been separated, it is possible to perform the substrate thinning process which causes little damage to a terminal section, or the like, formed on the pair of substrates having been separated.
Still further, in the invention it is preferable that the encapsulating means is formed in the same step as the step of forming the sealing resin layer on the one original substrate having an area for a plurality of display devices.
That is to say, since the encapsulating means is formed in the same step as the step of forming the sealing resin layer, it is not necessary to add a new step, and it is possible to easily form the encapsulating means on the edge of the pair of substrates having been separated.
Still further, in the invention it is preferable that a plurality of display sections and driving circuit sections for supplying signals to the display section are respectively formed on the one original substrate having an area for a plurality of display devices, and the sealing resin layer is placed around each display section while the encapsulating means is placed around each driving circuit section.
That is to say, since the sealing resin layer is placed around each display section and the encapsulating means is placed around each driving circuit section, it is possible even in a driving circuit integral-type display device to implement the substrate thinning process in a simple manner without causing damage to the driving circuit sections formed on the substrate.
Still further, in the invention it is preferable that the substrate holding means is a substrate cassette capable of storing a plurality of pairs of substrates having been separated to be of a size of each individual display device.
That is to say, since the substrate holding means is a substrate cassette which is capable of storing a plurality of pairs of substrates having been separated, damage to the substrates is minimized, and it is possible to perform the thinning process of a plurality of display appaatuses in a simple manner.
Still further, in the invention it is preferable that the other original substrate which is bonded onto the one original substrate having an area for a plurality of display devices via the sealing resin layer has an area for substantially one display device.
That is to say, since the other original substrate which is bonded onto the one original substrate having an area for a plurality of display devices has an area for substantially one display device, it is not necessary to bond the other substrate onto a portion opposed to a faulty component of a display device, and it is possible to bond the other substrate only onto conforming items, whereby it is possible to enhance the conforming item factor of display device.
Still further, in the invention it is preferable that before the substrate thinning process, a liquid crystal material is injected into a gap surrounded by the sealing resin layer between the pair of substrates having been separated to be of a size of each individual display device.
That is to say, injection of a liquid crystal material into the gap between the pair of substrates having been separated makes it possible to efficiently produce a low-profile and lightweight liquid crystal display device.
Since performing the step of injecting a liquid crystal material before the substrate thinning process makes it possible to perform injection of liquid crystal in a state where the pair of substrates having been separated have not been thinned, the substrates would not be broken or chipped in the step of injecting liquid even when a liquid crystal material is injected by the vacuum injection method.
The invention provides a method for producing a display device composed of at least a pair of substrates, the method comprising the step of performing a substrate thinning process of, in a state where a plurality of pairs of substrates which respectively be of a size of each individual display device are held by substrate holding means, thinning at least one substrate of each pair of substrates.
According to the invention, in the method for producing a display device, the substrate thinning process is performed in a state where the plurality of pairs of substrates which respectively be of a size of each individual display device are held by the substrate holding means. For this reason, in the method for producing a display device according to the invention, it is possible to use a smaller etching tank than that used for performing a thinning process in a state of an assembly of devices, and hence the required quantity of an etchant for the substrate thinning process is less than the required quantity thereof for the thinning process performed in a state of an assembly of devices. In addition, the plurality of pairs of substrates are subjected to the thinning process at a time, so that the throughput of the thinning process is enhanced as compared with a case of thinning the plurality of pairs of substrates one by one, and hence it is possible to perform the thinning process in an efficient manner. As a result, it is possible to easily implement a more lightweight and lower-profile display device than a display device according to the prior art.
In the invention it is preferable that before the step of performing the substrate thinning process the respective pairs of substrates are bonded to each other via a sealing material and encapsulating means is placed at an end portion of the respective pairs of substrates,
the encapsulating means encapsulates a space between the pair of substrates; and
the encapsulating means is placed in the step of placing the sealing material between the pair of substrates.
According to the invention, in the method for producing a display device, the encapsulating means and the sealing material are formed in the same step. For this reason, it is not necessary to add an extra step of forming the encapsulating means to the steps of producing a display device, so that it is possible to form the encapsulating means at the end portion of the pair of substrates in a simple manner.
In the invention it is preferable that before the step of performing the substrate thinning process a display section including a component related to display and a driving circuit section for supplying signals to the display section are formed between the respective pairs of substrates,
the sealing material is placed around the display section; and
the encapsulating means is placed around the driving circuit section.
According to the invention, in the method for producing a display device, the encapsulating means is formed around the driving circuit section of the pair of substrates bonded by the sealing material. For this reason, also in a driving circuit integral-type display device, it is possible to perform the substrate thinning process in a simple manner without causing damage to the driving circuit section formed on the pair of substrates.
In the invention it is preferable that the substrate holding means is a substrate cassette capable of holding the plurality of pairs of substrates of a size of each individual display device at a time.
According to the invention, in the method for producing a display device, the plurality of pairs of substrates are held in the substrate cassette at a time. As a result, damage to the substrates is minimized, so that it is possible to perform the process of thinning the plurality of pairs of substrates in a simple manner.
In the invention it is preferable that the method for producing a display device further comprises the step of sealing in a liquid crystal material between the pair of substrates.
According to the invention, in the method for producing a display device, the liquid crystal material is sealed in between the pair of substrates, whereby it is possible to efficiently produce a more lightweight and lower-profile liquid crystal display device than a liquid crystal display device according to the prior art. The injection step of the liquid crystal material is preferably performed before the substrate thinning process, whereby it is possible to inject liquid crystal in a state where the thickness of the pair of substrates is more than that of a completed liquid crystal display device. As a result, the substrates would not be broken or chipped in the injection step of liquid crystal even when the liquid crystal material is injected by the vacuum injection method, so that it is possible to produce a liquid crystal display device in a more efficient manner.